Benzo-(h)-quinoline-5-ol is prepared by heating together 4-amino-2-naphthalenesulphonic acid, glycerol, concentrated sulphuric acid, and picric acid, and fusing the product with sodium hydroxide. Benzo-(h)-quinoline-6-ol is similarly prepared. Benzo-(h)-quinoline-6 : 9-diol is prepared by fusing benzo-(h)-quinoline-6 : 9-disulphonic acid with potassium hydroxide and sodium hydroxide. Benzo-(h)-quinoline-5 : 9-diol is similarly prepared. Benzo-(h)-quinoline-6 : 9-disulphonic acid is prepared by heating together 4-aminonaphthalene - 1 : 6 - disulphonic acid, glycerol, concentrated sulphuric acid, and picric acid. 9 - Hydroxybenzo - (h) - quinoline - 5 - sulphonic acid and -6-sulphonic acid are similarly prepared. 4 - Aminonaphthalene - 1 : 6 - disulphonic acid is obtained by dissolving Dahl's acid (a crude mixture of 4-aminonaphthalene-1 : 6- and -1 : 7-disulphonic acids) in hot water with the aid of sodium acetate, and treating the filtered solution with a large excess of acetic acid and crystallizing. The crystalline cake obtained is dissolved in hot water containing ammonium hydroxide to make a neutral solution and is saturated with calcium chloride and the calcium salt crystallized. The calcium salt is converted to the potassium salt and the solution of the latter obtained is acidified with excess acetic acid and allowed to crystallize. 9 - Aminobenzo - (h) - quinoline - 6 - ol is prepared by heating potassium 9-aminobenzo-(h)-quinoline-6-sulphonate with potassium hydroxide solution in an autoclave, filtering, acidifying, and finally salting out with anhydrous sodium sulphate. Potassium 9 - aminobenzo - (h) - quinoline-6-sulphonate is prepared by heating in an autoclave a mixture of 9-hydroxybenzo-(h)-quinoline-6-sulphonic acid, aqueous ammonium hydroxide, and aqueous sulphur dioxide, and finally precipitating with potassium chloride. 9 - Acetylaminobenzo - (h) - quinoline - 6 - ol is prepared by acetylating 9-aminobenzo-(h)-quinoline-6-ol using excess of acetic anhydride in the presence of aqueous sodium carbonate. 9 - Acetylaminobenzo - (h) - quinoline - 6 - ol-A-sulphonic acid is similarly prepared. 9 - Aminobenzo - (h) - quinoline - 6 - ol - X-sulphonic acid is prepared by sulphonating 9-aminobenzo-(h)-quinoline-6-ol hydrochloride. 9 - p - Toluenesulphonylaminobenzo - (h)-quinoline - 6 - ol - X - sulphonic acid is prepared by reacting 9-aminobenzo-(h)-quinoline-6-ol-X-sulphonic acid in hot sodium acetate solution with p-toluenesulphonyl chloride. 9 - Octadecylsulphonylaminobenzo - (h) - quinoline-6-ol-X-sulphonic acid is prepared by adding a pyridine solution of octadecylsulphonyl chloride dropwise to a pyridine solution of 9-aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid and refluxing. 9-Tetradecylsulphonylbenzo - (h) - quinoline - 6 - ol - X - sulphonic acid and 9-(31-nitrobenzenesulphonyl)-aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid are similarly prepared. 9 - (31 - Aminobenzenesulphonyl) - aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid is prepared by reducing 9-(31-nitrobene-sulphonyl) - aminobenzo - (h) - quinoline - 6-ol-X-sulphonic acid with an aqueous solution of sodium hydrosulphite and sodium hydroxide. 9 - (31 - Tetradecanoylaminobenzenesulphonyl)-aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid is prepared by adding a benzene solution of myristoyl chloride dropwise to a benzene-pyridine pyridine solution of 9-(31-aminobenzenesulphonyl) - aminobenzo - (h)-quinoline-6-ol-X-sulphonic acid. 9 - (71 - Carboxy - 21 - naphthyl) - aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid is prepared by refluxing together a mixture of water, sodium hydroxide, 7-hydroxy-2-naphthoic acid, 9 - aminobenzo - (h) - quinoline - 6-ol-X-sulphonic acid, and sodium metabisulphite. 9 - 21 - [71 - (111 - Octadecyl - 511 - sulpho - 211-benzimidazolyl) - phenylcarbamyl] - naphthylaminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid is prepared by refluxing together pyridine, benzene, 9 - (71 - carboxynaphthyl)-aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid, and 1-octadecyl-2-(41-aminophenyl) - benzimidazole - 5 - sulphonic acid, removing part of the mixed solvent by distillation, and adding a benzene solution of phosphorus trichloride. 9 - 21 - [71 - (111 - Methyl - 611-myristoylamino - 411 - sulpho) - phenylcarbamyl]-naphthylaminobenzo - (h) - quinoline - 6 - ol - X-sulphonic acid is similarly prepared. 9 - Methylaminobenzo - (h) - quinoline - 6 - ol is prepared by heating together in an autoclave a mixture of benzo-(h)-quinoline-9-ol-6-sulphonic acid, aqueous methylamine solution, and saturated sulphur dioxide solution to obtain 9 - methylaminobenzo - (h) - quinoline-6-sulphonic acid, and heating the latter in an autoclave with aqueous potassium hydroxide. 7 - Carboxybenzo - (h) - quinoline - 6 - ol is prepared by heating together 7-cyanobenzo-(h)-quinoline-6-sulphonic acid and aqueous potassium hydroxide in an autoclave and acidifying. 7 - Cyanobenzo - (h) - quinoline - 6 - sulphonic acid is prepared by diazotizing acidified 7-aminobenzo - (h) - quinoline - 6 - sulphonic acid, adding the diazonium salt to an aqueous solution of cuprous cyanide and sodium cyanide, salting out, and purifying. 7 - Aminobenzo - (h) - quinoline - 6 - sulphonic acid is prepared by reducing with iron and acetic acid 7-nitrobenzo-(h)-quinoline-6-sulphonic acid, itself prepared by nitrating benzo-(h)-quinoline-6-sulphonic acid with nitric and sulphuric acids. 9 - [21 - (41:61 - dimethylamino - 1:3:5-triazinylamino)] - benzo - (h) - quinoline - 6 - ol-X-sulphonic acid is prepared by reacting 9-aminobenzo - (h) - quinoline - 6 - ol - X - sulphonic acid with cyanuric chloride in presence of aqueous potassium hydroxide, and then heating with aqueous methylamine solution. 6 - Aminobenzo - (h) - quinoline - 9 - ol and 6:9 - diaminobenzo - (h) - quinoline are prepared by heating together benzo-(h)-quinoline-6:9-diol, concentrated ammonium hydroxide, and aqueous sulphur dioxide in an autoclave, and are separated. 6 - p - Toluenesulphonamidobenzo - (h) - quinoline-9-ol is prepared by refluxing together 6-aminobenzo - (h) - quinoline - 9 - ol hydrochloride, pyridine, and benzene, adding p-toluenesulphonyl chloride dissolved in benzene, and heating. 9 - (81 - Carboxymethoxy - 2 - naphthylamino)-benzo - (h) - quinoline - 6 - ol - X - sulphonic acid is prepared by refluxing together the sodium salts of 8-carboxymethoxy-2-naphthylamine and 6 - hydroxy - 9 - aminobenzo - (h) - quinoline-X-sulphonic acid in aqueous sodium bisulphite solution. 9 - Methanesulphonamidobenzo - (h) - quinoline-6-ol-X-sulphonic acid is prepared by reacting 9 - aminobenzo - (h) - quinoline - 6 - ol-X-sulphonic acid in pyridine or aqueous alkaline solution with methanesulphonyl chloride. 6 - Methanesulphonamidobenzo - (h) - quinoline - 9 - ol, 9 - p - toluenesulphon - N - methylamidobenzo - (h) - quinoline - 6 - ol, and 6 - p-toluenesulphonamidobenzo - (h) - quinoline - 9 - ol are similarly prepared, 9 - Methanesulphonamido - 6 - aminobenzo-(h)-quinoline is prepared by heating with ammonium hydroxide solution and sodium bisulphite solution in an autoclave 9-methanesulphonamidobenzo - (h) - quinoline - 6 - ol, itself obtained by reacting 9-aminobenzo-(h)-quinoline-6-ol with methanesulphonyl chloride in pyridine solution. 10 - Aminobenzo - (h) - quinoline - 6 - ol is prepared by heating with potassium hydroxide in an autoclave 10-aminobenzo-(h)-quinoline-6-sulphonic acid, itself prepared by reducing with iron and water 10-nitrobenzo-(h)-quinoline-6-sulphonic acid. The latter is separated as the more insoluble sodium salt from a mixture with 7 - nitrobenzo - (h) - quinoline - 6 - sulphonic acid obtained by nitrating with fuming nitric acid in cold concentrated sulphuric acid benzo-(h)-quinoline-6-sulphonic acid, obtained by the Skraup reaction from 1-aminonaphthalene-4-sulphonic acid. Specifications 644,863 and 649,811 are referred to.